Phebalium calcicola (Rutaceae: Boronieae): a species described as new, restricted to south-eastern South Australia, is proposed as Critically Endangered

Phebalium calcicola, a multi-stemmed shrub from south-eastern South Australia, is segregated from the P. squamulosum subsp. squamulosum assemblage and described here as new, based on phenetic distinctness, habitat preference and geographical disjunction. It is compared with P. squamulosum subsp. squamulosum s.str. from the Sydney region, as well as the geographically closest populations from Victoria, which are currently referred as P. squamulosum subsp. squamulosum. A recommendation for the conservation status of this species as Critically Endangered is proposed. An amended key to species of Phebalium in South Australia is provided.